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Posted to mapreduce-issues@hadoop.apache.org by "Kannan Rajah (JIRA)" <ji...@apache.org> on 2015/01/31 01:12:35 UTC

[jira] [Created] (MAPREDUCE-6237) DBRecordReader is not thread safe

Kannan Rajah created MAPREDUCE-6237:
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             Summary: DBRecordReader is not thread safe
                 Key: MAPREDUCE-6237
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6237
             Project: Hadoop Map/Reduce
          Issue Type: Bug
    Affects Versions: 2.5.0
            Reporter: Kannan Rajah
            Assignee: Kannan Rajah


DBInputFormat.createDBRecorder is reusing JDBC connections across
instances of DBRecordReader. This is not a good idea. We should be creating separate connection. If performance is a concern, then we should be using connection pooling instead.

I looked at DBOutputFormat.getRecordReader. It actually creates a
new Connection object for each DBRecordReader. So can we just change
DBInputFormat to create new Connection every time?

The connection reuse code was added as part of connection leak bug in 
MAPREDUCE-1443. Any reason for caching the connection?



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